1. Field of the Invention
This invention relates to contact lenses, and more specifically to multi-focal contact lenses having an ellipsoid shape and improved translation control.
2. Description of the Related Art
Numerous versions of hard and soft, single-focus and multifocal contact lenses are available today. Multifocal lenses may have sharply defined transitions between the corrective elements, or may have a more gradual transition zone. Baron et al. disclose a lens having a vertical transition zone. Multifocal lenses are generally kept in proper rotational orientation on the eyeball by ballasting the lower part of the lens, by using thin zones beneath the eyelids, or by the overall geometry of the lens. Jacobstein, e.g., discloses a ballasted lens having a pressure-releasing vent.
No contact lens which is commercially available or disclosed in any of the patents known to Applicant includes a truncated ellipsoid shape to provide improved translational characteristics together with an arcuate junction between vision correcting components.
Applicant is aware of the following U.S. patents, disclosed by a pre-examination search:
______________________________________ U.S. Pat. No. Issue Date Patentee ______________________________________ 3,031,927 May 1, 1962 Wesley 3,037,425 Jun. 5, 1962 De Carle 3,279,878 Oct. 18, 1966 Long 4,549,794 Oct. 29, 1985 Losbaek, et al. 4,573,775 Mar 4, 1986 Bayshore 4,618,227 Oct. 21, 1986 Bayshore 4,618,228 Oct. 21, 1986 Baron, et al. 4,6l8,229 Oct. 21, 1986 Jacobstein, et al. 4,693,572 Sep. 15, 1987 Tsuetaki, et al. 4,728,182 Mar. 1, 1988 Kelman 4,938,583 Jul. 3, 1990 Miller 5,071,244 Dec. 10, 1991 Ross 5,141,301 Aug. 25, 1992 Morstad 5,173,723 Dec. 22, 1992 Volk 5,245,366 Sep. 14, 1993 Svochak 5,245,367 Sep. 14, 1993 Miller, et al. ______________________________________